Cooling roof construction

ABSTRACT

A cooling roof construction comprising a substantially horizontal roof having a weatherproof membrane, and where a perforated tile layer is arranged a distance above said membrane, where the space between the membrane and the perforated tile layer is connected by at least one conduit to an outside ambient space.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Danish Patent Application No. PA 2013 70274 filed on May 22, 2013, the entire contents of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a cooling roof construction as well as a method of cooling buildings utilizing such a roof construction.

BACKGROUND OF THE INVENTION

With the increasing focus on energy consumption there is a desire to lower the energy consumption and thereby the cost of energy in connection with among other things buildings, living quarters, etc.

For houses the object is to maintain an interior climate which is neither too cold nor too hot and as such during winter periods it is necessary to heat the houses and during summer periods it is desirable to cool the houses. In a number of regions the costs of cooling houses exceed by far the costs of heating houses. Furthermore, it is more energy consuming to cool the interior of houses than it is to heat the same house.

It is known in the art to provide a perforated upper roofing layer, see for example U.S. Pat. No. 4,674,249. This construction is provided in order to decrease damage to underlying roofing constructions, and to further provide ventilation to the underlying roof construction, for example in order to remove water ingressed into the underlying structure.

OBJECT OF THE INVENTION

The present invention provides a low cost solution, especially for cooling of houses. The invention is especially used for buildings having a flat or substantially flat roof. The invention is based on the principle that the sun will heat the flat roof surfaces whereby the solar heating will penetrate the roof construction and into the building thereby increasing the interior temperature.

DESCRIPTION OF THE INVENTION

In this connection the invention provides a cooling roof construction comprising a substantially horizontal roof having a weatherproof membrane, and where a perforated tile layer is arranged a distance above said membrane, where the space between the membrane and the perforated tile layer is connected by at least one conduit to an outside ambient space outside the roof's perimeter or above the tile layer.

Be creating a perforated tile area arranged a distance above the roof construction as such a space between the roof construction and the perforated tiles is created. The air inside this space will be heated by the solar influx, i.e. solar energy and due to the basic principles of hot air rising relative to cooler air the air in the space will move upwards, i.e. away from the roof surface through the perforations in the tiles. During this movement an under-pressure will occur between the perforated tiles and the roof surface which will cause fresh air to be sucked into the space. As this air has not been heated by the solar influx, the net result will be that air in the space will have a substantially lower temperature than air immediately above a fully exposed roof surface. Therefore, the perforated tile layer will create a cooling mechanism whereby the solar influx, i.e. the solar energy, will not be able to penetrate into the roof construction and thereby heat the interior of the building.

Furthermore by directing the conduit to be connected to an ambient space, for example the free air on the side of the building, the space between the roofing membrane and the tiles is provided with fresh air, and not recirculation of the air “trapped” in the space between the roofing membrane and the tiles. In this manner, better ventilation and thereby cooling is achieved.

In a further advantageous embodiment the perforated tile layer is assembled from a plurality of tiles, where the tiles are elevated relative to the membrane by means of risers.

By using a plurality of tiles the elevated tile layer is relatively easy to install in that it is possible to select tiles which have a size which may easily be carried and manually handled on the roof surface. Examples of such tiles are disclosed in U.S. Pat. No. 5,509,244 but it should be understood that naturally the invention is not limited to the use of this type of tiles, but tests clearly indicate that these tiles are very useful for obtaining the cooling properties of the present invention.

One further advantage of using tiles as suggested in U.S. Pat. No. 5,509,244 is the size of the perforations. Naturally other tiles having substantially corresponding perforation sizes may also be used. The perforations has a size such that when snow falls on the tiles, the snow will accumulate on the top side of the tiles, leaving the space between the roof structure and the tiles free from snow. This space will contain an amount of non-moving air, which effectively will act as extra insulation. Consequently, during hot periods, cool air will be provided helping to cool the building whereas during cold periods with snow fall, the snow will help insulate the building. Both situations will decrease the energy needed to respectively cool or heat the building.

In the same context risers as suggested in EP1192323 may also be used with good results. The advantages of using the risers in the European patent provides the elevated layer with large versatility in that different tile sizes may be used and the tile layer may be arranged horizontally regardless of the slant of the underlying roof structure, naturally within limits, simply by using more or less risers. In this manner it is possible to convert a relatively useless slanting/flat roof into a useful outdoor space.

In a further advantageous embodiment of the invention the risers have different height, such that the tile layer is a slanted or horizontal surface. These advantages are already described above and the risers may be constructed as suggested above by superposing a plurality of riser elements or by manufacturing risers as single elements having various heights. In a further advantageous embodiment of the invention the ambient space to which the conduit is connected is at a lower elevation or cooler space than the space between the membrane and the tile layer. As an under-pressure is created due to the solar energy heating the air trapped between the perforated tile layer and the roof construction air movement is created by the influx of solar energy. By connecting a conduit to the air volume between the perforated tile layer and the roof construction the air movement will cause air movement in the conduit. By connecting the other end of the conduit to a place with cooler air for example at a lower elevation or a cooler space such as for example an area which will be in shadow or a cellar space, ground well or the like, cooler air will be sucked into the space between the perforated tile layer and the roof construction and as such will further improve the lowering of the temperature on the roof and thereby the influx of heat into the interior of the building which will again lower the cost of cooling the interior of the building.

In a further advantageous embodiment of the invention the tiles and/or risers made from plastics, preferably in an injection moulding process. By using the risers and tiles suggested above these are plastic moulded elements which are constructed such that they will be able to provide the necessary load carrying characteristics in order to provide a useful surface. However, this is not necessary in all instances and as such also weaker tile elements and smaller risers may be used in order to provide the same advantages as already described above. The injection moulding process is a relatively cheap manufacturing process and as such together with the relatively low cost of installing such a roof an over-all cheap but very effective cooling installation may be achieved.

In a still further advantageous embodiment temperature controlled valve means are provided near the outlet of the conduit.

The means for controlling the valves may be but not limited to metal springs which are made from materials having specific temperature expansion/contraction properties, such as the valves are set to remain closed and only open when the temperature in the volume between the roof and the tiles rises above 20 degrees centigrade. The valves themselves may be simple dampers, plates or the like which may be brought from a position obstructing the conduit to a position where the air may flow freely through the conduit, and any position in between.

The present invention is also directed to a method of cooling a building using a cooling roof construction as already described above. Naturally the advantages already discussed above will also be achieved with the method.

DESCRIPTION OF THE DRAWING The invention will now be described with reference to the accompanying drawings where

FIG. 1 illustrates a schematic cross-section through a roof structure of a building.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 is illustrated a schematic cross-section through a roof structure of a building. The building 1 in this embodiment has a substantially flat roof structure 2. The roof structure is provided with the normal membranes etc. in order to render it watertight. These features are not illustrated as they are not important for the invention.

Above the roof structure 2 is arranged a number of perforated tiles 3 which tiles 3 are elevated relative to the roof structure by means of risers 4. In this embodiment the risers 4 are illustrated as comprising a number of superposed elements, but they may also be constructed simply by single element risers. Furthermore, a conduit 5 is arranged in connection with the space 6 created between the plurality of tiles 3 and the roof construction 2. The risers will only support corners of the tiles such that a substantially free space 6 is created between the roof structure 2 and the tiles 3.

As the solar energy illustrated by the arrows 7 impacts on the tiles 3 air trapped in the spaces 6 will be heated and thereby move upwards through the perforations 8 provided in the tiles as illustrated by the arrows 10. Consequently, an under-pressure will occur in the space 6 whereby air will be sucked through the conduit 5 as illustrated by the arrow 9. By arranging the inlet 5′ of the conduit 5 in a suitable place where the air is cooler, for example from a basement, cellar, ground well or a shadow section behind the building 1, the air introduced into the spaces 6 due to the suction created by the under-pressure will be substantially cooler and thereby hinder the solar energy 7 in penetrating through the roof structure 2 and into the building proper. In this manner a very simple low-cost and no running cost cooling system is provided.

Further the outlet 5″ is provided with a valve 11. The valve 11, is activated by a temperature sensitive mechanism, which will not be further elaborated. Any suitable operation mechanism, mechanical or electrical may naturally be employed. The valve mechanism 11 may for example be programmed to be shut until the temperature in the space 6 rises above 20 degrees, after which the valve 11 opens and allows cool air to be sucked into the space through the conduit 5. 

1. A cooling roof construction comprising a substantially horizontal roof having a weatherproof membrane, and where a perforated tile layer is arranged a distance above said membrane, where the space between the membrane and the perforated tile layer is connected by at least one conduit to an outside ambient space outside the roof's perimeter or above the tile layer.
 2. The cooling roof construction according to claim 1 wherein the perforated tile layer is assembled from a plurality of tiles, where the tiles are elevated relative to the membrane by means of risers.
 3. The cooling roof construction according to claim 2 wherein the risers have different height, such that the tile layer is a slanted or horizontal surface.
 4. The cooling roof construction according to claim 1 wherein the ambient space to which the conduit is connected is at a lower elevation or cooler space than the space between the membrane and the tile layer.
 5. The cooling roof construction according to claim 1 wherein the tiles and/or risers are made from plastics, preferably in an injection moulding process.
 6. The cooling roof construction according to claim 1 wherein temperature controlled valve means are provided near the outlet of the conduit.
 7. Method of cooling a building having a substantially flat roof space, where at least one perforated tile is arranged at a distance above the roof, and where cooler air by means of a conduit is guided into the space created between the roof and the perforated tile.
 8. Method according to claim 7 wherein the cooler air is obtained from a lower elevation, a cellar space, a well or the like, and by natural convection transported to the space between the roof and the perforated tile, where the cooler air is heated due to the exposure to solar heating of the tile surface, where after the air escapes upwards through the perforations in the tiles creating under-pressure in the space between the roof and the tiles, thereby creating air movement. 